CN1661390A - Method for automatic determination of the sagittal plane - Google Patents

Abstract

In a method and magnetic resonance apparatus for the automatic determination of the sagittal plane in the examination region of an object, an essentially coronal localizer image exposure of the examination region is acquired, from which the sagittal plane is determined by an automatic image assessment by the image-processing unit of the magnetic resonance apparatus.

Description

Method for automatic determination of the sagittal plane

technical field

The invention relates to a method for automatically determining the sagittal plane of a region of an object to be examined by means of a magnetic resonance apparatus.

Background technique

In the context of the acquisition of images of the examination object by means of a magnetic resonance system, specific information about the examination object is required in order to know the position of the examination object relative to the coordinate system of the magnetic resonance system and to be able to precisely define the plane of the tomographic image to be recorded. Knowledge of the location of the preferred plane is important. Furthermore, knowledge of this marked plane is also important in order to be able to record tomographic images that can be compared in repeated examinations.

One such plane is the sagittal plane, where the term "sagittal plane" is understood to mean every body plane that is parallel to the center plane of the body or the sagittal suture of the cranium. In the prior art, the determination of the sagittal plane or sagittal position is performed manually. First of all, the most precise positioning of the examination object in the MRI system, for example the patient whose spine is to be imaged, means that the medical technical assistant should take care that the patient is lying supine as straight and flat as possible location. Several reference photographs are then taken, if necessary for example with different contrasts for the T1, T2 or T2 ^* values. Usually the number of reference photographs is 3-5, which are then reproduced for the doctor, who determines the state of the sagittal or centrosagittal position by optical analysis combined with his expertise. Given the curvature of the spine, the physician either tries to find a compromise setting, or applies a compromise setting according to the equipment manufacturer's settings. On the one hand, this method is very expensive and on the other hand it is relatively error-prone, since on the one hand errors can occur during the positioning of the patient which lead to calculation problems in subsequent recordings, and on the other hand difficulties arise from time to time in the image calculations , especially when the image quality is poor or contains no or only insufficient image information important for determining the sagittal position.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method that facilitates the determination of the sagittal plane in order to simplify the setting process of the subsequent imaging sagittal slice.

In order to solve this technical problem, in a method of the type mentioned at the outset, it is proposed according to the invention to take a substantially coronal localizer picture of the examination region, from which picture is automatically detected by the image processing unit of the magnetic resonance device. Image analysis to determine the sagittal plane.

In order to support and simplify the determination of the plane, the invention proposes to determine the plane fully automatically by means of a suitable analysis of an overview image taken as quickly as possible, wherein the overview image photo is called a "locator photo" and by means of which the important inspection area. These image prints are then processed and analyzed by the image processing unit of the magnetic resonance system using suitable evaluation algorithms in order to determine the mean sagittal image position and the inclination of the sagittal plane relative to the system coordinate system. This means that it is not necessary to take multiple overview images as in the prior art, but by taking a so-called "single shot turbo spin echo sequence (Single Shot Turbo Spinecho Sequenz)" is sufficient for automatic planar Sure. Furthermore, the doctor is no longer required to carry out the plane determination, although the parallel determination of the plane, for example from the locator photographs, and the checking of the results of the automatic analysis are naturally reserved for the doctor. Overall, a considerable simplification of the plane determination process and a considerable time reduction are achieved by the method according to the invention.

As mentioned above, any analysis algorithm may be used for the image analysis of the localizer photographs, as long as these algorithms are suitable for determining the sagittal position and generating the sagittal plane therefrom. It is expedient here if the plane is determined on the basis of an analysis of the gray value distribution or brightness distribution in the image or in one or more marked image regions. Alternatively, it is also conceivable to determine the plane on the basis of a pattern recognition analysis of the image or one or more marked image regions for the determination of anatomical landmarks. The algorithm for the latter application depends on the inspection area. The selection of the algorithm to be used can be carried out by the image processing unit itself (as long as it is provided with the localizer image for the analysis), or it can be preset on the device side by the corresponding input of the doctor for the examination region to be imaged. Certainly.

Problems arise especially with regard to correct and reproducible setting of the sagittal plane when performing spine imaging of the entire spine region, ie in the cervical, thoracic and lumbar region. In order to determine the plane as precisely as possible during this examination, in a preferred development of the inventive concept, the spine or the vertebral segment is recorded in such a way that the fluid-filled spinal cavity is located in the localizer picture, wherein the localizer picture is taken in such a way , so that the areas filled with liquid appear optically prominent, in particular brighter. This is based on the idea that the position or plane can be determined with sufficient precision due to the spinal cavity running through the middle of the spine. In order to make it available for processing in the automatic image analysis, the positioner pictures are taken in such a way that the liquid or the fluid area is clearly displayed brighter than the background. For this purpose, corresponding recording parameters are selected for the recording sequence. Effective measurement times in such locator shots should be in the range of about one second.

It is expedient to calculate a gray value distribution or a brightness distribution in at least two mutually separated transverse image planes of the recorded localizer image for determining the plane, and to obtain the result in accordance with the recording technique proposed according to the invention for optically highlighting the spinal cord. The sagittal plane is determined by the gray value or brightness maximum value in the at least two transverse image planes. In order to determine the plane as precisely as possible, the gray value distribution or brightness distribution can also be determined in more than two transverse image planes. The corresponding sagittal position can then be precisely determined by determining the position of the maximum or sagittal plane.

For example, in the case of an inclination or curvature of the spine, it may be possible that two or even more gray-scale values or Brightness maximum. This may also depend on the position of the examination area and the plane, for example the recording of the patient's cervical region and the position of the transverse image plane close to the transition to the skull. In this case, it is expedient to create a maximum mean value from two or more grayscale or brightness maxima, which is then used to determine the plane, and if necessary to weight the individual maxima accordingly.

Especially at a given spinal inclination, for example due to an imprecise positioning of the patient in the device, or an anatomical curvature of the spine, it may occur that the maximum value or the mean value of the maximum values does not lie on the common path as ideally connection line. In this case, the connecting line and the actual sagittal plane resulting from it are determined by interpolation among the existing maximum values to be processed.

In addition to the examination of the spine in particular, the determination of the sagittal plane is also important in the acquisition of other objects, for example the examination of the knee. In this case, the automatic determination of the sagittal plane according to the invention is carried out by determining the posterior condyles of the femur as anatomical landmarks. In this case, it is expedient first to determine a line connecting the two condyles, perpendicular to which the position of the sagittal plane is determined. That is, here the determination of the plane is carried out on the basis of pattern recognition and anatomical labeling, where another parameter setting is selected for the locator image. In this case, a localizer recording is first performed in the form of a T1 measurement and analysis.

It is also expedient according to the invention to automatically determine the coronal plane in addition to the sagittal plane. In this case, the determination of the coronal plane is preferably based on a substantially uncurved vertebral region during the spine examination, which is possible for a naturally S-shaped spine, primarily in the thoracic region, which is substantially straight over a sufficient section spread out. During the knee examination, the coronal plane is expediently determined on the basis of a line that can be determined between the two condyles. In each case it is preferred to also use or take into account the determined position data of the sagittal plane when determining the coronal plane.

In order to ensure that, in particular in the case of spine recordings, the examination area also actually shows all relevant regions for the automatic determination of the plane, the positioner should be appropriately recorded with a slice thickness of 40 mm to 100 mm, in particular between 60 mm and 80 mm. photo. That is to say, a thick-slice coronal image, by which it is ensured that, especially in the case of the spine, despite the curvature of the spine, due to the selected slice thickness, a strong spinal cavity can be captured in the image in segments with a diameter of at most approximately 1 cm.

In addition to the method according to the invention, the invention also relates to a magnetic resonance system which, together with its image recording unit, is designed for an automatic plane determination in accordance with the method described above.

Description of drawings

Further advantages, features and details of the invention emerge from the following description of embodiments and figures. In the figure,

1 shows a schematic diagram of a magnetic resonance system according to the invention for carrying out the method according to the invention,

2 shows a schematic diagram of the captured vertebral region with highlighted vertebral cavity and gray value or brightness characteristics in the first transverse image plane,

Figure 3 shows the gray value or brightness distribution in the second transverse image plane in Figure 2,

Figure 4 shows the gray value or brightness distribution in the third transverse image plane in Figure 3,

Figure 5 shows the position of the mid-sagittal slice plane determined from the determined maximum value.

Detailed ways

FIG. 1 shows a magnetic resonance apparatus 1 according to the invention, comprising an examination unit 2 into which a patient is pushed and a controller 3 with an integrated image processing unit 4 for controlling the operation of the entire apparatus, wherein the image processing unit 4 Configuration for image acquisition, image processing and image analysis operations, as well as for implementing the method of the invention described below. Furthermore, a display 5 on which the generated image is output is provided.

Image processing unit 4 is designed to implement the method according to the invention for automatic determination of the sagittal plane. To this end, localizer image acquisitions are first performed in the form of thick-slice coronal single-shot fast spin echo (Single Shot Turbo Spinecho) localizer acquisitions. This acquisition takes place coronally with a slice thickness of, for example, 60 mm to 80 mm and optionally fixed slice positions, ie no manual slice positioning is required. Depending on the examination region to be recorded, the field of view (ie the image recording region) corresponds to the usual effective measurement, but can also be somewhat smaller. However, a larger field of view can also be provided in the event of a large curvature of the spine to be expected.

In order to record the spine with the spinal cavity or the spinal cord displayed in an optically prominent display required for the subsequent image analysis, the operating parameters required for the image recording are set accordingly. For fast image capture set the TE value to about 500ms, the fat saturation setting on the spectrum can usually be omitted for fast measurements without compromising image quality.

The image shown as an example in FIG. 2 is obtained after recording a very short locator measurement (the effective measurement time of which is approximately 1 second). The image is then analyzed by the image processing unit 4 to automatically determine the sagittal plane. For this purpose, a gray value characteristic or an intensity characteristic or a brightness characteristic of the pixels of the digital image is determined and calculated on different transverse image planes.

FIG. 2 shows the gray value characteristic or intensity characteristic V1 determined during the evaluation of the pixel contents of the transverse image plane B1. Clearly, a stronger peak P1 or convex maximum is shown in the region of the spinal cavity S relative to the position of the image plane B1, the position of which is given by the line shown on the image plane B1 and marked with M1.

FIG. 3 shows the locator photograph LB recorded in FIG. 2 , wherein gray values or brightness distributions V2 are likewise determined here for the second image plane B2 indicated by the corresponding horizontal line. Here, too, a prominent peak P1 is displayed in the region of the spinal cavity S with the maximum value M2 at a given position on the line of the image plane B2.

Correspondingly, in FIG. 4 the procedure as in FIG. 3 is also carried out for the image plane B3 marked by a line with respect to the locator image LB. Here, however, two peaks P3a and P3b are shown in the region of the spinal cavity S, which result in two maxima M3a and M3b. From these two maxima M3 a and M3 b , a maximum mean value M3 is determined, optionally by different weighting (for example according to the intensity of the peaks), which is marked on the line of the transverse plane B3 .

From FIG. 5 it can be seen how to determine the position of the sagittal plane from the maximum value. The localizer picture LB is shown again, in which the respective maximum value M1 , M2 and M3 is shown for each image plane B1 , B2 and B3 respectively. In the example shown, all three maxima M1 , M2 and M3 lie near a common line L which simultaneously defines a sagittal plane SE perpendicular thereto. In this way, the center of the vertebral segment and the optimal sagittal profile in the sagittal plane can be determined automatically and rapidly in the described manner by determining the intensity or gray value maxima accordingly and, if necessary, by evaluating the individual features with a weighting algorithm. The slope (Kippung). The determined slice positions and possible inclinations of the vertebral segment centers are then copied into the usage log for the subsequent tomography acquisition. That is to say, the mid-sagittal change of the spinal cavity determined in this way and thus the center of the sagittal guidance are used as setting parameters for the subsequent image acquisition.

As mentioned above, the maximum values M1 , M2 and M3 shown in FIG. 5 are ideally located near the connecting line L . In cases of strong curvature or tilt of the spine, these maxima do not necessarily lie on a common line, but are offset from it. The determination of the line takes place by (possibly weighted) interpolation, that is, to determine the position of the line L and thus the sagittal plane SE, the positions of the individual maxima can be applied with different intensities to the interpolation algorithm .

Depending on specific position parameters for the sagittal plane SE, it is also possible to determine the position of the coronal plane relative to the examination region. The same principle that applies to spine imaging in the examination of relatively straight, largely uncurved vertebral segments can also be applied to the thoracic spine, the coronal plane being perpendicular to the sagittal plane.

Claims (15)

1. sagittal method that is used for automatically determining the subject area checked by means of magnetic resonance device, it is characterized in that, take the crown steady arm photo of being essentially of a width of cloth inspection area, determine sagittal plane by the automated image analysis of the graphics processing unit of magnetic resonance device according to this photo.

2. method according to claim 1, it is characterized in that, determining on analysis foundation of described plane to grey value profile in image or the one or more image-region that marks or Luminance Distribution, or on the basis of the pattern recognition analysis of being determined anatomical landmarks being used in image or the one or more image-region that marks, realize.

3. method according to claim 1 and 2, it is characterized in that, the subject area that will take in image is vertebra or the vertebra fragment that has the vertebra chamber of filling liquid, wherein, take the steady arm photo like this, make this fill region of fluid and optically show outstandingly, particularly brighter.

4. method according to claim 3 is characterized in that, determines grey value profile or Luminance Distribution in order to determine the plane at least two separated landscape images planes, and determines sagittal plane according to gray-scale value or brightness maximal value.

5. method according to claim 4 is characterized in that, determines grey value profile or Luminance Distribution in more than two landscape images planes.

6. according to claim 4 or 5 described methods, it is characterized in that, a landscape images plane highlight filling and having in the region of fluid under two or more gray-scale values or the peaked situation of brightness, obtain maximal value mean value and be used for determining the plane.

7. according to each described method in the claim 4 to 6, it is characterized in that, according to connecting determined maximal value, being the line of the maximal value mean value of a plane of delineation in case of necessity, perhaps the line of determining by interpolation according to its position is determined described sagittal plane.

8. method according to claim 1 and 2 is characterized in that the subject area that will take is a knee in image, wherein, come automatically to determine sagittal plane by femoral back joint is defined as anatomical landmarks.

9. method according to claim 8 is characterized in that, at first determines a line that connects two joints in order to determine the plane, vertically determines sagittal position with this line.

10. each described method in requiring according to aforesaid right is characterized in that, except described sagittal plane is also automatically determined coronal-plane.

11. method according to claim 10 is characterized in that, determines described coronal-plane according to a unbending basically vertebra zone in the vertebra inspection.

12. method according to claim 11 is characterized in that, also determines described coronal-plane according to determined sagittal position data.

13. method according to claim 10 is characterized in that, determines described coronal-plane according to the line that can determine in the knee inspection between two joints.

14., it is characterized in that described steady arm photo is to utilize 40mm to 100mm, the particularly bed thickness between 60mm to 80mm to take according to each described method in the aforesaid right requirement.

15. a magnetic resonance equipment, its structure are used for implementing according to each described method in the aforesaid right requirement.

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